Abstract 199: TGF-β in exosomes facilitates HNSCC progression by accelerating tumor angiogenesis

TGF-β is a key regulator for tumor initiation and progression in head and neck squamous cell carcinoma (HNSCC). Tumor-derived exosomes (TEX) contain TGF-β and accumulate in the tumor microenvironment (TME). This study characterizes the TGF-β content of HNSCC-derived exosomes and evaluates in vitro and in vivo TGF-β signaling by exosomes that results in promotion of angiogenesis. TEX were isolated from supernantants of 5 different HNSCC cell lines by mini size exclusion chromatography (mini-SEC) and characterized by electron microscopy, nanoparticle tracking analysis and mass spectrometry (LC-MS/MS). TGF-β content in exosomes was evaluated by immunoblotting. Proliferation and migration of SVEC4-10 lymphendothelial cells in response to TEX were investigated in vitro and results were confirmed in vivo, using a matrigel plug model in mice. In these experiments a novel trivalent TGF-β receptor trap (mRER) was used to inhibit TGF-β signaling. TGF-β levels and activity were similarly measured in exosomes isolated from plasma of 20 HNSCC patients. TEX carried high levels of TGF-β and were found to be potent inducers of angiogenesis in vitro and in vivo through functional reprogramming and phenotypic modulation of endothelial cells. Proliferation (p<0.01) and migration (p<0.01) by SVEC4-10 were stimulated by TEX and effects were inhibited by mRER treatment of SVEC4-10 (p<0.05). TEX promoted formation of defined vascular structures in vivo, and increased (p<0.001) vascularization in matrigel plugs relative to control. Those effects were inhibited by mRER treatment (p<0.05). Exosomes in plasma of HNSCC patients carried varying levels of TGF-β, and patients with nodal metastases had elevated TGF-β levels (p<0.01) relative to patients with no meastasis.The data show that TGF-β signaling by TEX in HNSCC promotes angiogenesis and drives tumor progression. Future efforts should focus on silencing TEX, thereby adding new options to existing anti-angiogenic therapies.

Citation Format: Nils Ludwig, Saigopalakrishna S. Yerneni, Cynthia S. Hinck, Monika Pietrowska, Andrew P. Hinck, Theresa L. Whiteside. TGF-β in exosomes facilitates HNSCC progression by accelerating tumor angiogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 199.

Abstract 993: Chemotherapy enhances exosome secretion via upregulation of cholesterol metabolism in acute myeloid leukemia

Therapies for Acute Myelogenous Leukemia (AML) have not been successful largely due to disease recurrence after chemotherapy. Recent studies showed that exosomes play a significant role in leukemia chemo-resistance. Levels of exosomes in patients’ plasma are elevated at AML diagnosis relative to those in normal donors’ plasma and remain elevated when patients reach complete remission (CR). These exosomes carry immunosuppressive molecules, interfere with anti-leukemia immunity and promote blast chemoresistance. We hypothesized that the development of methods for blocking exosome secretion could benefit AML patients. To understand the mechanisms of enhanced exosome secretion in AML blasts, we focused on cholesterol synthesis in blasts and its relationship to exosome secretion. Cholesterol metabolism in AML cell lines after treatment of chemotherapeutic agents (cytarabine and decitabine) was shown to enhance (p<0.005) intracellular level of cholesterol and the expression of HMGCR (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase), the rate-limiting enzyme in cholesterol synthesizing mevalonate pathway. Consequently, the production of exosomes in the cell culture supernatants increased (p<0.02). Treatment with an HMGCR inhibitor, simvastatin, or siRNAs targeting HMGCR blocked (p<0.02) the chemotherapy- induced enhancement of exosome production. Exosomes carry HMGCR and chemotherapy enhanced HMGCR levels on exosomes. Our results show that chemotherapy enhances exosome secretion by increasing cholesterol synthesis in leukemic blasts. A pharmacologic blockade of HMGCR with simvastatin emerges as a potential future therapeutic for exosomes in AML.

Note: This abstract was not presented at the meeting.

Citation Format: Chang-Sook Hong, Emily J. Jeong, Beatrice Razzo, Michael Boyiadzis, Theresa L. Whiteside. Chemotherapy enhances exosome secretion via upregulation of cholesterol metabolism in acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 993.

Abstract 3091: Effects of melanoma cell-derived exosomes in melanoma patients’ plasma on immune cell functions

Background: Exosomes are a subset of small (30-150nm) extracellular vesicles (EVs) of the endocytic origin that mediate intercellular communication in health and disease. Exosomes are actively produced by tumor cells, circulate freely in body fluids and carry messages that alter functions of normal cells in the tumor microenvironment (TME), including immune cell functions. The ability of melanoma exosomes to reprogram immune cell functions might contribute to disease progression.

Methods: To evaluate effects of melanoma cell-derived exosomes (MTEX) on human immune cell subsets, we isolated exosomes from plasma of 12 patients with melanoma and separated MTEX from non-MTEX by immune capture using anti-CSPG4 mAb on beads. These exosome fractions, and exosomes from plasma of 6 normal donors used as controls (NC), were studied by on-bead flow cytometry to quantify their surface protein profiles and in co-incubation assays with immune cell subsets for functional attributes. Phenotypic and functional profiles of MTEX and non-MTEX were compared.

Results & Conclusion: MTEX were enriched (p<0.005)( in FasL and TRAIL, induced apoptosis of CD8+T cells, down-regulated CD69 expression levels on T cells and inhibited their proliferation (all p<0.0005). MTEX also interfered with NK cell functions (p<0.001). Non-MTEX were enriched (P<0.005) in co-stimulatory proteins, CD40L, OX40L, OX40 and, similar

to exosomes of NC, were not immunosuppressive. Thus, MTEX, present in excess in plasma of patients with metastatic melanoma, mediate immune suppression and contribute to immune escape of the tumor.

Citation Format: Priyanka Sharma, Brenda Diergaarde, Soldano Ferrone, John M. Kirkwood, Theresa L. Whiteside. Effects of melanoma cell-derived exosomes in melanoma patients’ plasma on immune cell functions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3091.

Circulating exosomes measure responses to therapy in head and neck cancer patients treated with cetuximab, ipilimumab, and IMRT

Purpose: Exosomes, small extracellular vesicles (EVs) derived from the endocytic compartment of their parent cells, are present in plasma of cancer patients and may serve as non-invasive biomarkers of disease outcome. Here, we asked whether tumor-derived (TEX) and/or T-cell derived exosomes can predict outcome in head and neck squamous cell carcinoma (HNSCC) patients treated with oncological therapy.

Materials and Methods: 18 HNSCC patients enrolled in phase I clinical trial and receiving a combination of cetuximab, ipilimumab and radiation therapy were serially monitored for TEX and T cell-derived exosomes. Exosomes isolated from plasma by size exclusion chromatography were fractionated into TEX and CD3 + T cell-derived exosomes by immunocapture. Exosome-associated proteins were quantified by on-bead flow cytometry. Exosome molecular cargos of patients whose tumors recurred within 2 years (N = 5) were compared to cargos of patients who remained disease free at 2 years (N = 13) after therapy.

Results: The predictive value of the exosome molecular cargo for disease recurrence was evaluated pre-, during and post therapy. In patients whose disease recurred, total exosome proteins, TEX/total exosome ratios, total CD3+, CD3(-)PD-L1+ and CD3 + 15s+ (Treg-derived) exosomes increased from the baseline levels. In patients who remained disease free, total exosome protein and TEX levels decreased, CD3+ and CD3+ CD15s+ exosomes stabilized and CD3+ CTLA4+ exosomes declined after ipilimumab therapy.

Conclusion: TEX and T cell-derived circulating exosomes instead of immune cells were used for monitoring of patients’ responses to oncological therapy. The results support the potential role of exosomes as a non-invasive tumor and immune cell biomarkers in cancer.

Proteomes of exosomes from HPV(+) or HPV(-) head and neck cancer cells: differential enrichment in immunoregulatory proteins

Human papillomavirus (HPV) is an etiologic factor in head and neck squamous cell carcinoma (HNSCC). HPV(+) cancers respond favorably to therapy potentially due to more robust anti-tumor immune responses. We hypothesized that tumor-derived exosomes (TEX) produced by HPV(+) or HPV(-) HNSCCs differentially modulate anti-tumor immune responses.

Proteomes of exosomes from HPV(+) and HPV(-) HNSCC cell lines were compared in search for proteins putatively involved in the communication with immune system. TEX were isolated from supernatants of HPV(+) (SCC-2, SCC-47, and SCC-90) or HPV(-) (PCI-13 and PCI-30) cells by size exclusion chromatography. A comparison of proteome profiles was performed by high-resolution mass spectrometry. The presence and biological activity of selected immunoregulatory proteins were validated by flow cytometry and co-incubation assays. Exosomes produced by SCC-90 and PCI-30 cells contained 711 proteins, including 80 proteins specific for HPV(+) exosomes and 77 specific for HPV(-) exosomes, associated with similar GO terms such as regulation of cell growth, metabolism, communication, and cellular signaling. Search for proteins localized in the membrane and involved in immune regulation identified a few proteins detected specifically in HPV(+) or HPV(-) exosomes. Only HPV(+) exosomes were enriched in immune effector cell-related CD47 and CD276 antigens; only HPV(-) exosomes contained tumor-protective/growth-promoting antigens, MUC-1 and HLA-DA. Flow cytometry and Western blots confirmed the reciprocal presence/paucity of these proteins in a whole panel of tumor cells and corresponding exosomes. The differential content of protein cargos in HPV(+) and HPV(-) exosomes might contribute to the disparity in immune responses that characterize HPV(+) and HPV(-) HNSCC.

Optimization of cell culture conditions for exosome isolation using mini-size exclusion chromatography (mini-SEC)

Extracellular vesicles (EVs) are emerging as a major intercellular communication system engaged in a variety of physiological and pathophysiological processes. Tumor-derived exosomes (TEX) are a subset of EVs of special interest as potential cancer biomarkers. Supernatants of tumor cell lines are widely used as the source of pure TEX for molecular/genetic studies. To optimize TEX isolation and characterization for these studies, we evaluated culture conditions for different tumor cell lines and used mini size exclusion chromatography (mini-SEC) for TEX isolation. Each tumor cell line showed unique culture requirements that determined the recovery, purity and total yield of TEX. Culture conditions for optimal TEX purity and recovery by mini-SEC could be modified by altering the media composition and numbers of seeded cells. TEX recovered from mini-SEC fraction #4 under optimized conditions were biologically active, were sized from 30 to 150 nm in diameter, had a typical vesicular morphology and carried endocytic markers. The most critical requirement for reproducible exosome recovery was re-seeding of tumor cells in numbers adjusted to reflect the optimized culture conditions for each tumor cell line. This study provides insights into a cell culture technique, which can be optimized for exosome production by various human or mouse tumor cell lines for isolation by mini-SEC.

An Interferon-Driven Oxysterol-Based Defense against Tumor-Derived Extracellular Vesicles

Tumor-derived extracellular vesicles (TEV) "educate" healthy cells to promote metastases. We found that melanoma TEV downregulated type I interferon (IFN) receptor and expression of IFN-inducible cholesterol 25-hydroxylase (CH25H). CH25H produces 25-hydroxycholesterol, which inhibited TEV uptake. Low CH25H levels in leukocytes from melanoma patients correlated with poor prognosis. Mice incapable of downregulating the IFN receptor and Ch25h were resistant to TEV uptake, TEV-induced pre-metastatic niche, and melanoma lung metastases; however, ablation of Ch25h reversed these phenotypes. An anti-hypertensive drug, reserpine, suppressed TEV uptake and disrupted TEV-induced formation of the pre-metastatic niche and melanoma lung metastases. These results suggest the importance of CH25H in defense against education of normal cells by TEV and argue for the use of reserpine in adjuvant melanoma therapy.

The potential of tumor-derived exosomes for noninvasive cancer monitoring: an update

Introduction: Liquid biopsy platforms are being actively developed in the biomarker field. Extracellular vesicles (EVs), especially the tumor-derived exosome (TEX) subsets of EVs, represent a platform that allows for molecular and genetic profiling of parent tumor cells. TEX are ubiquitous in body fluids of cancer patients and are promising clinically relevant surrogates of cancer cells. Areas covered: Isolation from body fluids of cancer patients and subsetting of exosomes based on immunoaffinity capture offers a means of evaluating proteins, lipids, nucleic acids and other molecular contents that are a characteristic of TEX and exosomes produced by reprogrammed normal cells. The same liquid biopsy can inform about the status of a tumor and simultaneously evaluate the competency of immune cells to mediate anti-tumor activities. Expert commentary: TEX and reprogrammed non-TEX isolated from plasma of cancer patients have the potential to become non-invasive biomarkers of cancer diagnosis, prognosis and response to therapies.

Harmonization of exosome isolation from culture supernatants for optimized proteomics analysis

Exosomes, the smallest subset of extracellular vesicles (EVs), have recently attracted much attention in the scientific community. Their involvement in intercellular communication and molecular reprogramming of different cell types created a demand for a stringent characterization of the proteome which exosomes carry and deliver to recipient cells. Mass spectrometry (MS) has been extensively used for exosome protein profiling. Unfortunately, no standards have been established for exosome isolation and their preparation for MS, leading to accumulation of artefactual data. These include the presence of high-abundance exosome-contaminating serum proteins in culture media which mask low-abundance exosome-specific components, isolation methods that fail to yield “pure” vesicles or variability in protein solubilization protocols. There is an unmet need for the development of standards for exosome generation, harvesting, and isolation from cellular supernatants and for optimization of protein extraction methods before proteomics analysis by MS. In this communication, we illustrate the existing problems in this field and provide a set of recommendations that are expected to harmonize exosome processing for MS and provide the faithful picture of the proteomes carried by exosomes. The recommended workflow for effective and specific identification of proteins in exosomes released by the low number of cells involves culturing cells in medium with a reduced concentration of exosome-depleted serum, purification of exosomes by size-exclusion chromatography, a combination of different protein extraction method and removal of serum-derived proteins from the final dataset using an appropriate sample of cell-unexposed medium as a control. Application of this method allowed detection of >250 vesicle-specific proteins in exosomes from 10 mL of culture medium.

Molecular and Functional Profiles of Exosomes From HPV(+) and HPV(-) Head and Neck Cancer Cell Lines

Exosomes produced by tumor cells have been shown to reprogram functions of human immune cells. Molecular cargos of exosomes isolated from supernatants of HPV(+) and HPV(−) head and neck cancer (HNC) cell lines or from HNC patients' plasma were compared. The exosome protein profiles resembled those of respective parent tumor cells. Only HPV(+) exosomes carried E6/E7, p16, and survivin. HPV(−) exosomes were negative for cyclin D1 and carried low p53 levels. Immunomodulatory molecules (TGF-β, FasL, OX40, OX40L, and HSP70) were carried by HPV(+) and HPV(−) exosomes. These exosomes co-incubated with human T cells induced apoptosis and suppressed T cell activation and proliferation. HPV(−) exosomes suppressed DC maturation and expression of antigen processing machinery (APM) components. In contrast, HPV(+) exosomes promoted DC maturation and did not suppress expression of APM components in mature DCs. While DCs readily internalized exosomes, T lymphocytes resisted their uptake during the initial 12 h co-culture. Thus, HPV(+) exosomes capable of sustaining DC functions may play a key role in promoting anti-tumor immune responses thereby improving outcome in patients with HPV(+) cancers.

Exosomes in HNSCC plasma as surrogate markers of tumour progression and immune competence

Exosomes in plasma of head and neck squamous cell carcinoma (HNSCC) patients comprise subsets of vesicles derived from various cells. Recently, we separated CD3⁽⁺⁾ from CD3^(-) exosomes by immune capture. CD3^(-) exosomes were largely tumour-derived (CD44v3⁺ ). Both subsets carried immunosuppressive proteins and inhibited functions of human immune cells. The role of these subsets in immune cell reprogramming by the tumour was investigated by focusing on the adenosine pathway components. Spontaneous adenosine production by CD3⁽⁺⁾ or CD3^(-) exosomes was measured by mass spectrometry, as was the production of adenosine by CD4⁺ CD39⁺ regulatory T cells (T_reg ) co-incubated with these exosomes. The highest level of CD39/CD73 ectoenzymes and of adenosine production was found in CD3^(-) exosomes in patients with the stages III/IV HNSCCs). Also, the production of 5'-AMP and purines was significantly higher in T_reg co-incubated with CD3^(-) than CD3⁽⁺⁾ exosomes. Consistently, CD26 and adenosine deaminase (ADA) levels were higher in CD3⁽⁺⁾ than CD3^(-) exosomes. ADA and CD26 levels in CD3⁽⁺⁾ exosomes were significantly higher in patients with early (stages I/II) than advanced (stages III/IV) disease. HNSCC patients receiving and responding to photodynamic therapy had increased ADA levels in CD3⁽⁺⁾ exosomes with no increase in CD3^(-) exosomes. The opposite roles of CD3⁽⁺⁾ ADA⁺ CD26⁺ and CD3^(-) CD44v3⁺ adenosine-producing exosomes in early versus advanced HNSCC suggest that, like their parent cells, these exosomes serve as surrogates of immune suppression in cancer.

Metabolic reprogramming of stromal fibroblasts by melanoma exosome microRNA favours a pre-metastatic microenvironment

Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear. We investigated whether Human Melanoma-derived exosomes (HMEX) could reprogram human adult dermal fibroblasts (HADF) and cause extracellular acidification. HMEX were isolated from supernatants of six melanoma cell lines (3 BRAF V600E mutant cell lines and 3 BRAF wild-type cell lines) using ultracentrifugation or Size Exclusion Chromatography (SEC). Rapid uptake of exosomes by HADF was demonstrated following 18 hours co-incubation. Exposure of HDAF to HMEX leads to an increase in aerobic glycolysis and decrease in oxidative phosphorylation (OXPHOS) in HADF, consequently increasing extracellular acidification. Using a novel immuno-biochip, exosomal miR-155 and miR-210 were detected in HMEX. These miRNAs were present in HMEX from all six melanoma cell lines and were instrumental in promoting glycolysis and inhibiting OXPHOS in tumour cells. Inhibition of miR-155 and miR-210 activity by transfection of miRNA inhibitors into HMEX reversed the exosome-induced metabolic reprogramming of HADF. The data indicate that melanoma-derived exosomes modulate stromal cell metabolism and may contribute to the creation of a pre-metastatic niche that promotes the development of metastasis.

Exosomes from HNSCC Promote Angiogenesis through Reprogramming of Endothelial Cells

For solid tumors, such as head and neck squamous cell carcinoma (HNSCC), an adequate blood supply is of critical importance for tumor development and metastasis. Tumor-derived exosomes (TEX) accumulate in the tumor microenvironment (TME) and serve as a communication system between tumor and normal stromal cells. This study evaluates in vitro and in vivo effects mediated by TEX that result in promotion of angiogenesis. TEX produced by PCI-13 (HPV^-) and UMSCC47 (HPV⁺) cell lines or from plasma of HNSCC patients were isolated by mini size exclusion chromatography (mini-SEC). TEX morphology, size, numbers, and molecular profile were characterized, and the angiogenesis-inducing potential was measured in arrays and real-time PCR with human endothelial cells (HUVEC). Uptake of labeled TEX by HUVECs was demonstrated by confocal microscopy. Tube formation, proliferation, migration, and adherence by HUVECs in response to TEX were investigated. The 4-nitroquinoline-1-oxide (4-NQO) oral carcinogenesis mouse model was used to confirm that TEX induce the same results in vivo TEX were found to be potent inducers of angiogenesis in vitro and in vivo through functional reprogramming and phenotypic modulation of endothelial cells. TEX carried angiogenic proteins and were internalized by HUVECs within 4 hours. TEX stimulated proliferation (P < 0.001), migration (P < 0.05), and tube formation (P < 0.001) by HUVECs and promoted formation of defined vascular structures in vivo The data suggest that TEX promote angiogenesis and drive HNSCC progression. Future efforts should focus on eliminating or silencing TEX and thereby adding new options for improving existing antiangiogenic therapies.Implications: TEX appear to play an important role in tumor angiogenesis and thus may contribute to tumor growth and metastasis of HNSCC in this context. Mol Cancer Res; 16(11); 1798-808. ©2018 AACR.

Abstract 2049: HNSCC-derived exosomes promote angiogenesis and tumor progression through reprogramming of the tumor microenvironment in vitro and in vivo

Head and neck squamous cell carcinoma (HNSCC) is the seventh most common malignant disease. For solid tumors, such as HNSCC, an adequate blood supply is of critical importance for tumor development, growth and metastasis. Tumor-derived exosomes (TEX) accumulate in the tumor microenvironment (TME) and serve as a communication system between the tumor and normal stromal cells. TEX may be one of the mechanisms responsible for induction of tumor angiogenesis. This study evaluates in vitro and in vivo effects mediated by TEX that result in promotion of tumor angiogenesis.

Biologically-active exosomes produced by SCC47 and PCI-13 tumor cell lines were isolated by mini size exclusion chromatography (mini-SEC). Exosomes were also isolated from plasma specimens of HNSCC patients or healthy donors. Exosome morphology, size and numbers were characterized using TEM and q-Nano. Molecular profiles were evaluated by western blots with the exosome-specific marker TSG101 blotted as control. The angiogenesis-inducing potential of TEX was measured in arrays with human endothelial cells (HUVEC). Uptake of labeled TEX by HUVEC cells was demonstrated by confocal microscopy. Proliferation, migration, chemotaxis and the tube formation by HUVECs in response to TEX were investigated. The matrigel plug model and the 4-nitroquinoline-1-oxide (4-NQO) oral carcinogenesis were used to confirm that exosomes induce the same results in vivo. In vitro and in vivo experiments were repeated with plasma-derived exosomes obtained from HNSCC patients and healthy donors.

TEX were found to be potent inducers of angiogenesis in vitro and in vivo through functional re-programming and phenotypic modulation of endothelial cells. HNSCC-derived exosomes carried angiogenesis markers (coagulation factor III, IGFBP-3, thrombospondin 1 and uPA) and were internalized by HUVECs within 4 h. Cell line derived exosomes stimulated proliferation (PCI-13 p &lt; 0.05; SCC47 p &lt; 0.01), migration (p &lt; 0.05) and tube formation (p &lt; 0.001) by endothelial cells and promoted formation of defined vascular structures in vivo. Proliferation, migration and tube formation of plasma-derived exosomes obtained from HNSCC patients were significantly enhanced compared to healthy donors' exosomes (p &lt; 0.05).

Our data suggest that HNSCC-derived exosomes promoting angiogenesis, are an adverse factor in carcinogenesis and a potential biomarker of angiogenesis. Moreover, future efforts should focus on eliminating or silencing TEX and thereby adding new options for improving existing anti-angiogenic therapies.

Citation Format: Nils Ludwig, Saigopalakrishna S. Yerneni, Beatrice M. Razzo, Theresa L. Whiteside. HNSCC-derived exosomes promote angiogenesis and tumor progression through reprogramming of the tumor microenvironment in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2049.

Abstract 1748: Head and neck cancer-derived exosomes facilitate carcinogenesis in the murine 4NQO chemically induced oropharyngeal cancer

Purpose: An increasing body of evidence suggests that tumor-derived exosomes (TEX) promote tumor formation and progression. This study aims to show that exosomes produced by the SCCVII murine tumor cell line promote progression of pre-malignant oropharyngeal lesions to malignant tumors. The 4-Nitroquinoline 1-oxide (4NQO) tumor model is chemically induced in immunocompetent mice. It recapitulates all the histological stages and molecular changes associated with of oral carcinogenesis described for human head and neck squamous cell carcinoma (HNSCC). Experimental design: Exosomes were isolated from supernatant of a murine as well as human HNSCC cell-lines by mini size-exclusion chromatography (miniSEC). Morphology, number, protein and the molecular cargo of the recovered exosomes were determined. Exosome-mediated in vitro inhibition of lymphocyte proliferation and induction of CD8+ T-cell apoptosis were demonstrated. C57BL/6 mice were treated with 4NQO supplied in drinking water (100ug/ml) for 16 weeks and all developed oral and esophageal pre-malignant lesions. Exosomes were administered via a single tail-vein or retro-orbital injection at week 18. Tumor sizes and overall tumor burden per mouse were measured with a caliper. Proliferation indexes of individual tumors were measured by immunohistochemistry. Splenocytes were harvested and were analyzed for the presence and frequency of myeloid derived suppressor cells (MDSC) and Tregs, and for in vitro responsiveness of T cells to exogenous activators. Results: SCCVII-derived exosomes were found to carry an immunosuppressive cargo, including CD39, CD73, PD-L1, FasL and COX-2. One-time 90ug injections (IV) of exosomes to groups of &gt;8 mice induced a statistically significant increase in the number of developing tumors and in the overall tumor burden per mouse, relative to control mice injected with PBS. The average number of tumors per mouse was 6.3 versus 3.6, respectively (p &lt; 0.005). TEX derived from human HNSCC cell lines also induced a greater though not statistically significant number of tumors in 4NQO-treated mice. The MDSC frequency was increased in the exosome-injected mice relative to controls. The Treg frequency was not altered. Conclusions: The data demonstrate that the delivery of Head and Neck Cancer-derived exosomes enhanced carcinogenesis of the 4NQO-induced tumors in mice. Augmented carcinogenesis was associated with systemic immunosuppression and increases in the frequency of MDSCs in spleens of mice treated with exosomes.

Citation Format: Beatrice M. Razzo, Chang-Sook Hong, Kellsye P. Fabian, Nils Ludwig, Priyanka Sharma, Walter J. Storkus, Theresa L. Whiteside. Head and neck cancer-derived exosomes facilitate carcinogenesis in the murine 4NQO chemically induced oropharyngeal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1748.

IRX-2 natural cytokine biologic for immunotherapy in patients with head and neck cancers

Head and neck squamous cell carcinoma (HNSCC) is an immunosuppressive malignancy characterized by tumor-driven immune-system abnormalities that contribute to disease progression. For patients with surgically resectable HNSCC, treatment is often curative surgery followed by irradiation or chemoradiation in high-risk settings to reduce the risk of recurrence. Poor survival and considerable morbidity of current treatments suggest the need for new therapeutic modalities that can improve outcomes. Defects in antitumor immunity of HNSCC patients include suppressed dendritic cell (DC) maturation, deficient antigen-presenting cell function, compromised natural killer (NK)-cell cytotoxicity, increased apoptosis of activated T lymphocytes, and impaired immune-cell migration to tumor sites. Strategies for relieving immunosuppression and restoring antitumor immune functions could benefit HNSCC patients. IRX-2 is a primary cell-derived biologic consisting of physiologic levels of T-helper type 1 cytokines produced by stimulating peripheral blood mononuclear cells of normal donors with phytohemagglutinin. The primary active components in IRX-2 are IL2, IL1β, IFNγ, and TNFα. In vitro, IRX-2 acts on multiple immune-system cell types, including DCs, T cells, and NK cells, to overcome tumor-mediated immunosuppression. In clinical settings, IRX-2 is administered as part of a 21-day neoadjuvant regimen, which includes additional pharmacologic agents (low-dose cyclophosphamide, indomethacin, and zinc) to promote anticancer immunoresponses. In a Phase IIA trial in 27 patients with surgically resectable, previously untreated HNSCC, neoadjuvant IRX-2 increased infiltration of T cells, B cells, and DCs into tumors and was associated with radiological reductions in tumor size. Event-free survival was 64% at 2 years, and overall 5-year survival was 65%. Follow-up and data analysis are under way in the multicenter, randomized, Phase IIB INSPIRE trial evaluating the IRX-2 regimen as a stand-alone therapy for activating the immune system to recognize and attack tumors.

Microvessel density in head and neck squamous cell carcinoma

Purpose

Microvessel density (MVD) corresponds to the intensity of neo-angiogenesis. MVD assessments are based on the expression levels of the vascular endothelium markers such as, e.g., CD34 or CD105. The goal of this study was to assess MVD among patients with head and neck squamous cell carcinoma (HNSCC), and to evaluate the predictive value of MVD in head and neck cancers.

Methods

The study included 49 patients treated for HNSCC and 11 patients with dysplasia of the upper respiratory tract epithelium. Control tissues consisted of 12 normal mucous membranes of the throat. Expression levels of MVD markers were assessed by immunohistochemistry (IHC) using tissue microarrays (TMA). Clinicopathological factors and patients’ survival over the 5-year follow-up period were analyzed.

Results

The MVD/CD34 values were found to be significantly elevated in the HNSCCs compared to the non-malignant control tissues (p = 0.001) and to dysplastic tissues. (p = 0.02). Significantly higher MVD/CD105 values were also seen in the tumor compared to the control tissues (p = 0.001) or the dysplastic tissues (p = 0.001). Unexpectedly, significantly lower MVD/CD34 values were seen in the tumor tissues of patients with the T3–T4 tumors compared to those with T1–T2 tumors (p = 0.01).

Conclusions

HNSCCs have statistically higher MVD values compared to dysplasia of the upper respiratory tract epithelium. However, the MVD/CD34 values did not correlate with local invasiveness (the T feature) of HNSCCs. This counterintuitive observation suggests that assessments of MVD as performed on TMA by IHC using anti-CD34 or anti-CD105 antibodies considered to be specific for endothelial cell markers might underestimate the extent of the tumor vascularity in HNSCC.

Potential roles of tumor-derived exosomes in angiogenesis

INTRODUCTION

Tumor-derived exosomes (TEX) and their role in tumor progression by accelerating angiogenesis are of great current interest. A better understanding of the mechanisms underlying TEX-blood vessels cross-talk may lead to improvements in current diagnosis, prognosis and treatment of cancer. Areas covered: For solid tumors, an adequate blood supply is of critical importance for their development, growth and metastasis. TEX, virus-size vesicles which circulate freely throughout body fluids and accumulate in the tumor microenvironment (TME), have been recognized as a new contributor to angiogenesis. TEX serve as a communication system between the tumor and various normal cells and are responsible for functional reprogramming of these cells. The molecular and genetic cargos that TEX deliver to the recipient cells involved in angiogenesis promote its induction and progression. The targeted inhibition of TEX pro-angiogenic functions might be a novel therapeutic approach for control of tumor progression. Expert opinion: TEX circulating in body fluids of cancer patients carry a complex molecular and genetic cargo and are responsible for phenotypic and functional reprogramming of endothelial cells and other normal cells residing in the TME.

Plasma-derived Exosomes Reverse Epithelial-to-Mesenchymal Transition after Photodynamic Therapy of Patients with Head and Neck Cancer

Photodynamic therapy (PDT) is a palliative treatment option for head and neck squamous cell carcinoma (HNSCC) patients which induces local inflammation and alters tumor cell morphology. We show that exosomes in plasma of HNSCC patients undergoing PDT reprogram tumor cells towards an epithelial phenotype. Nine HNSCC patients were treated with PDT and plasma was collected prior to and at three timepoints after therapy. Exosome levels of E-Cadherin, N-Cadherin and TGF-β1 were tested by flow cytometry. Exosomes were co-incubated with cancer cells, and changes in expression of EMT markers were evaluated as were proliferation, migration, chemotaxis and invasiveness of tumor cells. Exosomes harvested pre- and 24h after PDT were enriched in N-Cadherin and TGF-β1. They induced the mesenchymal phenotype and up-regulated Vimentin and transcripts for Snail, Twist, α-SMA, Slug and ZEB1 in epithelial tumor cells. These exosomes also enhanced tumor proliferation, migration and invasion. In contrast, exosomes obtained on day 7 or 4-6 weeks after PDT carried E-cadherin, restored epithelial morphology and EpCAM expression in tumor cells, down-regulated expression of mesenchymal genes and inhibited proliferation, migration and invasion. The PDT-mediated conversion from the mesenchymal to epithelial tumor phenotype was mediated by exosomes, which also served as non-invasive biomarkers of this transition.

FOXP3+ Treg as a therapeutic target for promoting anti-tumor immunity

INTRODUCTION

Regulatory T cells (Treg) characterized by expression of FOXP3 and strong immunosuppressive activity play a key role in regulating homeostasis in health and disease. Areas covered: Human Treg are highly diverse phenotypically and functionally. In the tumor microenvironment (TME), Treg are reprogrammed by the tumor, acquiring an activated phenotype and enhanced suppressor functions. No unique phenotypic markers for Treg accumulating in human tumors exist. Treg are heterogeneous and use numerous mechanisms to mediate suppression, which either silences anti-tumor immune surveillance or prevents tissue damage by activated T cells. Treg plasticity in the TME endows them with dual functionality. Treg frequency in tumors associates either with poor or improved survival. Treg responses to immune checkpoint inhibition (ICI) differ from the restorative effects ICIs induce in other immune cells. Therapies used to silence Treg, including ICIs, are only partly successful. Treg persistence and resistance to depletion are critical for maintaining homeostasis. Expert opinion: Treg emerge as a heterogeneous subset of immunosuppressive T cells, which usually, but not always, favor tumor progression. Treg are also engaged in non-immune activities that benefit the host. Therapeutic silencing of Treg in cancer requires a deeper understanding of Treg activities in human health and disease.

Separation of plasma-derived exosomes into CD3(+) and CD3(-) fractions allows for association of immune cell and tumour cell markers with disease activity in HNSCC patients

Head and neck squamous cell carcinoma (HNSCC) is a highly immunosuppressive malignancy. Exosomes in HNSCC patients' plasma are enriched in inhibitory cargo and mediate immunosuppression. As these exosomes are products of various cells, the cellular origin of immunoregulatory proteins they carry is unknown. To test whether tumour- or T cell-derived exosomes in patients' plasma are immunosuppressive and impact upon disease activity, we separated CD3^(-) from CD3⁽⁺⁾ exosomes by immunocapture using anti-CD3 antibodies. The exosome protein cargo was evaluated for immunoregulatory proteins using on-bead flow cytometry. Tumour protein-enriched CD3^(-) exosomes were CD44v3⁽⁺⁾ . Surprisingly, mean levels of programmed death ligand 1 (PD-L1), cytotoxic T lymphocyte antigen 4 (CTLA-4) and cyclooxygenase-2 (COX-2) were similar in CD3⁽⁺⁾ and CD3^(-) exosomes, although the latter induced higher (P < 0·0025) ex-vivo apoptosis of CD8⁽⁺⁾ T cells and greater (P < 0·005) conversion of CD4⁺ T cells to CD4⁽⁺⁾ CD39⁽⁺⁾ regulatory T cells (T_reg ). CD3⁽⁺⁾ and CD3^(-) exosomes carrying high levels of immunosuppressive proteins were highly effective in mediating these functions. Exosomes of patients with Union for International Cancer Control (UICC) stages III/IV disease had higher levels of PD-L1 and COX-2 than stages I/II patients (P < 0·005). Patients with nodal involvement had exosomes with the higher inhibitory protein content than N0 patients (P < 0·03). CD3⁽⁺⁾ and CD3^(-) exosomes of HNSCC patients had higher PD-L1, COX-2 and CD15s levels than healthy donors' exosomes (P < 0·009), although levels of immunostimulatory OX40 or OX40L were not different. By isolating CD3^(-) /CD44v3-enriched and CD3⁽⁺⁾ exosomes from plasma, the cellular origins of immunoregulatory proteins they carry were identified. Association of exosome molecular profiles with disease progression supports the exosome potential as future cancer biomarkers.

Therapeutic reduction of cell-mediated immunosuppression in mycosis fungoides and Sézary syndrome

Tumor progression is associated with progressive immunosuppression mediated in part by T regulatory cell(s) (Treg) and/or myeloid-derived suppressor cell(s) (MDSC). Development of strategies to reduce populations of immune cells with suppressive function in cancer patients may enable the induction or recovery of immunity against tumor cells, which may limit or reverse disease progression. With a goal of developing Treg and MDSC neutralizing strategies to treat mycosis fungoides (MF) and Sézary syndrome (SzS), we determined the association between disease stage and suppressor cell populations in patients with MF/SzS, including those responding to therapy. We found elevations in Treg populations, across Treg subtypes, in patients with SzS, and these Treg markedly suppressed proliferation of autologous CD4+CD25- responder T cells. Interestingly, while MDSC numbers were not increased in MF/SzS patients, MDSC from patients with stage IB and above produced significantly more reactive oxygen species than those from stage IA MF patients and control cohorts. Therapy with the CD25-targeting agent denileukin diftitox or IFN-α2b was associated with a reduction in Treg numbers or MDSC function, respectively. These studies identify potential mechanisms of action for these therapies and support the development of coordinated strategies targeting both Treg and MDSC activities in patients with MF/SzS.

Immunoaffinity-based isolation of melanoma cell-derived exosomes from plasma of patients with melanoma

Tumour-derived exosomes (TEX) are a subset of extracellular vesicles (EVs) present in body fluids of patients with cancer. The role of this exosome subset in melanoma progression has been of interest ever since ex vivo studies of exosomes produced by melanoma cell lines were shown to suppress anti-melanoma immune responses. To study the impact of melanoma-derived exosomes (MTEX) present in patients’ plasma on melanoma progression, isolation of MTEX from total plasma exosomes is necessary. We have developed an immunoaffinity-based method for MTEX capture from plasma of melanoma patients. Using mAb 763.74 specific for the CSPG4 epitope uniquely expressed on melanoma cells, we separated MTEX from non-tumour cell-derived exosomes and evaluated the protein cargo of both fractions by quantitative flow cytometry. Melanoma-associated antigens were carried by MTEX but were not detectable in exosomes produced by normal cells. Separation of plasma-derived MTEX from non-MTEX provides an opportunity for future evaluation of MTEX as potential biomarkers of melanoma progression and as surrogates of melanoma in tumour liquid biopsy studies.

Head and Neck Carcinoma Immunotherapy: Facts and Hopes

Cancer of the head and neck (HNC) is a heterogeneous disease of the upper aerodigestive tract, encompassing distinct histologic types, different anatomic sites, and human papillomavirus (HPV)-positive as well as HPV-negative cancers. Advanced/recurrent HNCs have poor prognosis with low survival rates. Tumor-mediated inhibition of antitumor immune responses and a high mutational burden are common features of HNCs. Both are responsible for the successful escape of these tumors from the host immune system. HNCs evolve numerous mechanisms of evasion from immune destruction. These mechanisms are linked to genetic aberrations, so that HNCs with a high mutational load are also highly immunosuppressive. The tumor microenvironment of these cancers is populated by immune cells that are dysfunctional, inhibitory cytokines, and exosomes carrying suppressive ligands. Dysfunctional immune cells in patients with recurrent/metastatic HNC can be made effective by the delivery of immunotherapies in combination with conventional treatments. With many promising immune-based strategies available, the future of immune therapies in HNC is encouraging, especially as methods for genetic profiling and mapping the immune landscape of the tumor are being integrated into a personalized approach. Efficiency of immune therapies is expected to rapidly improve with the possibility for patients' selection based on personal immunogenomic profiles. Noninvasive biomarkers of response to therapy will be emerging as a better understanding of the various molecular signals co-opted by the tumors is gained. The emerging role of immunotherapy as a potentially beneficial addition to standard treatments for recurrent/metastatic HNC offers hope to the patients for whom no other therapeutic options exist. Clin Cancer Res; 24(1); 6-13. ©2017 AACR.

Exosome and mesenchymal stem cell cross-talk in the tumor microenvironment

Mesenchymal stem cells (MSCs) are a major component of the tumor microenvironment (TME) and play a key role in promoting tumor progression. The tumor uses exosomes to co-opt MSCs and re-program their functional profile from normally trophic to pro-tumorigenic. These tumor-derived small vesicles called "TEX" carry and deliver a cargo rich in proteins and nucleic acids to MSCs. Upon interactions with surface receptors on MSCs and uptake of the exosome cargo by MSCs, molecular, transcriptional and translational changes occur that convert MSCs into producers of factors that are necessary for tumor growth and that also alter functions of non-tumor cells in the TME. The MSCs re-programmed by TEX become avid producers of their own exosomes that carry and deliver mRNA and miRNA species as well as molecular signals not only back to tumor cells, directly enhancing their growth, but also horizontally to fibroblasts, endothelial cells and immune cells in the TME, indirectly enhancing their pro-tumor functions. TEX-driven cross-talk of MSCs with immune cells blocks their anti-tumor activity and/or converts them into suppressor cells. MSCs re-programmed by TEX mediate pro-angiogenic activity and convert stromal cells into cancer-associated fibroblasts (CAFs). Although MSCs have a potential to exert anti-tumor activities, they largely provide service to the tumor using the multidirectional communication system established by exosomes in the TME. Future therapeutic options consider disruption of this complex vicious cycle by either molecular or gene-regulated silencing of pro-tumor effects mediated by MSCs in the TME.

Clinical Significance of PD-L1+ Exosomes in Plasma of Head and Neck Cancer Patients

Purpose: The microenvironment of head and neck squamous cell carcinomas (HNSCC) is highly immunosuppressive. HNSCCs expressing elevated levels of PD-L1 have especially poor outcome. Exosomes that carry PD-L1 and suppress T-cell functions have been isolated from plasma of patients with HNSCC. The potential contributions of PD-L1⁺ exosomes to immune suppression and disease activity are evaluated.Experimental Design: Exosomes isolated from plasma of 40 HNSCC patients by size exclusion chromatography were captured on beads using anti-CD63 Abs, stained for PD-1 and PD-L1 and analyzed by flow cytometry. The percentages and mean fluorescence intensities (MFI) of PD-L1⁺ and PD-1⁺ exosome/bead complexes were correlated with the patients' clinicopathologic data. PD-L1^high or PD-L1^low exosomes were incubated with activated CD69⁺ human CD8⁺ T cells ± PD-1 inhibitor. Changes in CD69 expression levels on T cells were measured. Patients' plasma was tested for soluble PD-L1 (sPD-L1) by ELISA.Results: Levels of PD-L1 carried by exosomes correlated with patients' disease activity, the UICC stage and the lymph node status (P = 0.0008-0.013). In contrast, plasma levels of sPD-L1 or exosome PD-1 levels did not correlate with any clinicopathologic parameters. CD69 expression levels were inhibited (P < 0.03) by coincubation with PD-L1^high but not by PD-L1^low exosomes. Blocking of PD-L1⁺ exosome signaling to PD-1⁺ T cells attenuated immune suppression.Conclusions: PD-L1 levels on exosomes, but not levels of sPD-L1, associated with disease progression in HNSCC patients. Circulating PD-L1⁺ exosomes emerge as useful metrics of disease and immune activity in HNSCC patients.

SIGNIFICANCE

Circulating PD-L1^high exosomes in HNC patients' plasma but not soluble PD-L1 levels associate with disease progression. Clin Cancer Res; 24(4); 896-905. ©2017 AACR.

The effect of tumor-derived exosomes on immune regulation and cancer immunotherapy

Tumor-derived exosomes (TEX) carry both immunosuppressive and immunostimulatory receptor/ligands that in part mimic the profiles of the parent tumor cells. Operating as an intercellular communication system, TEX deliver protumor or antitumor signals to immune and nonimmune cells reprogramming their functions. Mechanisms responsible for cellular reprogramming include cell surface signaling and/or uptake of TEX by recipient cells. Once internalized, TEX transfer mRNA, miRNA and proteins that promote transcriptional/translational activities. TEX-mediated signaling is contextual and, in the tumor microenvironment, TEX largely mediate suppression. TEX may interfere with immune therapies either by sequestration of therapeutic antibodies or elimination of vaccine-induced or adoptively-transferred immune effector cells. TEX are emerging as an ubiquitous subcellular system regulating immune responses in patients with cancer.

Circulating exosomes carrying an immunosuppressive cargo interfere with cellular immunotherapy in acute myeloid leukemia

Exosomes, small (30–150 nm) extracellular vesicles (EVs) isolated from plasma of patients with acute myeloid leukemia (AML) carry leukemia-associated antigens and multiple inhibitory molecules. Circulating exosomes can deliver suppressive cargos to immune recipient cells, inhibiting anti-tumor activities. Pre-therapy plasma of refractory/relapsed AML patients contains elevated levels of immunosuppressive exosomes which interfere with anti-leukemia functions of activated immune cells. We show that exosomes isolated from pre-therapy plasma of the AML patients receiving adoptive NK-92 cell therapy block anti-leukemia cytotoxicity of NK-92 cells and other NK-92 cell functions. NK-92 cells do not internalize AML exosomes. Instead, signaling via surface receptors expressed on NK-92 cells, AML exosomes simultaneously deliver multiple inhibitory ligands to the cognate receptors. The signals are processed downstream and activate multiple suppressive pathways in NK-92 cells. AML exosomes reprogram NK-92 cells, interfering with their anti-leukemia functions and reducing the therapeutic potential of adoptive cell transfers. Plasma-derived exosomes interfere with immune cells used for adoptive cell therapy and may limit expected therapeutic benefits of adoptive cell therapy.

Human tumor-derived exosomes (TEX) regulate Treg functions via cell surface signaling rather than uptake mechanisms

Tumor-derived exosomes (TEX) are ubiquitously present in the tumor microenvironment and plasma of cancer patients. TEX carry a cargo of multiple stimulatory and inhibitory molecules and deliver them to recipient cells, serving as a communication network for the tumor. The mechanisms TEX use for delivering messages to recipient cells were evaluated using PKH26-labeled TEX produced by cultured human tumor cells, exosomes produced by dendritic cells-derived exosomes (DEX), or exosomes isolated from plasma of cancer patients (EXO). Human T-cell subsets, B cells, NK cells, and monocytes were co-incubated with TEX, DEX, or EXO and binding or internalization of labeled vesicles was evaluated by confocal microscopy and/or Amnis-based flow cytometry. Vesicle-induced Ca²⁺ influx in recipient T cells was monitored, and TEX-induced inosine production in Treg was determined by mass spectrometry. In contrast to B cells, NK cells or monocytes, conventional T cells did not internalize labeled vesicles. Minimal exosome uptake was only evident in Treg following prolonged co-incubation with TEX. All exosomes induced Ca²⁺ influx in T cells, with TEX and EXO isolated from cancer patients' plasma delivering the strongest, sustained signaling to Treg. Such sustained signaling resulted in the significant upregulation of the conversion of extracellular ATP to inosine (adenosine metabolite) by Treg, suggesting that TEX signaling could have functional consequences in these recipient cells. Thus, modulation of Treg suppressor functions by TEX is mediated by mechanisms dependent on cell surface signaling and does not require TEX internalization by recipient cells.

Immune Correlates of GM-CSF and Melanoma Peptide Vaccination in a Randomized Trial for the Adjuvant Therapy of Resected High-Risk Melanoma (E4697)

Purpose: E4697 was a multicenter intergroup randomized placebo-controlled phase III trial of adjuvant GM-CSF and/or a multiepitope melanoma peptide vaccine for patients with completely resected, high-risk stage III/IV melanoma.Experimental Design: A total of 815 patients were enrolled from December 1999 to October 2006 into this six-arm study. GM-CSF was chosen to promote the numbers and functions of dendritic cells (DC). The melanoma antigen peptide vaccine (Tyrosinase_{368-376 (370D)}, gp100_{209-217 (210M)}, MART-1_27-35) in montanide was designed to promote melanoma-specific CD8⁺ T-cell responses.Results: Although the overall RFS and OS were not significantly improved with the vaccine or GM-CSF when compared with placebo, immunomodulatory effects were observed in peripheral blood and served as important correlates to this therapeutic study. Peripheral blood was examined to evaluate the impact of GM-CSF and/or the peptide vaccine on peripheral blood immunity and to investigate potential predictive or prognostic biomarkers. A total of 11.3% of unvaccinated patients and 27.1% of vaccinated patients developed peptide-specific CD8⁺ T-cell responses. HLA-A2⁺ patients who had any peptide-specific CD8⁺ T-cell response at day +43 tended to have poorer OS in univariate analysis. Patients receiving GM-CSF had significant reduction in percentages of circulating myeloid dendritic cells (mDC) and plasmacytoid DC (pDC) at day +43. In a subset of patients who received GM-CSF, circulating myeloid-derived suppressor cells (MDSC), and anti-GM-CSF-neutralizing antibodies (Nabs) were also modulated. The majority of patients developed anti-GM-CSF Nabs, which correlated with improved RFS and OS.Conclusions: The assessment of cellular and humoral responses identified counterintuitive immune system changes correlating with clinical outcome. Clin Cancer Res; 23(17); 5034-43. ©2017 AACR.

Exosomes carrying immunoinhibitory proteins and their role in cancer

Recent emergence of exosomes as information carriers between cells has introduced us to a new previously unknown biological communication system. Multi-directional cross-talk mediated by exosomes carrying proteins, lipids and nucleic acids between normal cells, cells harbouring a pathogen or cancer and immune cells has been instrumental in determining outcomes of physiological as well as pathological conditions. Exosomes play a key role in the broad spectrum of human diseases. In cancer, tumour-derived exosomes carry multiple immunoinhibitory signals, disable anti-tumour immune effector cells and promote tumour escape from immune control. Exosomes delivering negative signals to immune cells in cancer, viral infections, autoimmune or other diseases may interfere with therapy and influence outcome. Exosomes can activate tissue cells to produce inhibitory factors and thus can suppress the host immune responses indirectly. Exosomes also promise to be non-invasive disease biomarkers with a dual capability to provide insights into immune dysfunction as well as disease progression and outcome.

Targeting adenosine in cancer immunotherapy: a review of recent progress

INTRODUCTION

The adenosine pathway plays a key role in modulating immune responses in health and in disease. In health, anti-inflammatory effects of adenosine balance pro-inflammatory ATP, limiting tissue destruction by activated immune cells. In disease, this balance is disturbed. Areas covered: This review focuses on cancer and explains how in the microenvironment, the ATP-adenosine balance shifts towards an excess of extracellular adenosine Expert commentary: The CD73-adenosine axis plays a key role in the inhibition of anti-tumor functions of immune effector cells. Today, adenosine emerges as one of the immune checkpoints that are implicated in the tumor escape from the host immune system. The adenosine pathway is currently viewed as a significant barrier to the effectiveness of immune therapies and becomes an important therapeutic target in cancer. Pharmacologic inhibitors or antibodies specific for the components of the adenosine pathways or adenosine receptors show efficacy in pre-clinical studies and are entering the clinical arena.

Suppression of Lymphocyte Functions by Plasma Exosomes Correlates with Disease Activity in Patients with Head and Neck Cancer

Purpose: Head and neck cancers (HNCs) often induce profound immunosuppression, which contributes to disease progression and interferes with immune-based therapies. Body fluids of patients with HNC are enriched in exosomes potentially engaged in negative regulation of antitumor immune responses. The presence and content of exosomes derived from plasma of patients with HNC are evaluated for the ability to induce immune dysfunction and influence disease activity.Experimental Design: Exosomes were isolated by size-exclusion chromatography from plasma of 38 patients with HNC and 14 healthy donors. Morphology, size, numbers, and protein and molecular contents of the recovered exosomes were determined. Coculture assays were performed to measure exosome-mediated effects on functions of normal human lymphocyte subsets and natural killer (NK) cells. The results were correlated with disease stage and activity.Results: The presence, quantity, and molecular content of isolated, plasma-derived exosomes discriminated patients with HNC with active disease (AD) from those with no evident disease (NED) after oncologic therapies. Exosomes of patients with AD were significantly more effective than exosomes of patients with NED in inducing apoptosis of CD8⁺ T cells, suppression of CD4⁺ T-cell proliferation, and upregulation of regulatory T-cell (Treg) suppressor functions (all at P < 0.05). Exosomes of patients with AD also downregulated NKG2D expression levels in NK cells.Conclusions: Exosomes in plasma of patients with HNC carry immunosuppressive molecules and interfere with functions of immune cells. Exosome-induced immune suppression correlates with disease activity in HNC, suggesting that plasma exosomes could be useful as biomarkers of HNC progression. Clin Cancer Res; 23(16); 4843-54. ©2017 AACR.

Biological Effects of Anti-Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) Antibody Formation in Patients Treated With GM-CSF (Sargramostim) as Adjuvant Therapy of Melanoma

OBJECTIVES

We investigated the development of binding and neutralizing antibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients receiving prolonged therapy with GM-CSF as adjuvant therapy of melanoma and the impact of these antibodies on biological effects.

METHODS

Fifty-three patients with high-risk melanoma that had been surgically excised were treated with GM-CSF, 125 μg/m daily for 14 days every 28 days for 1 year after surgical resection of disease. Serum samples for antibodies to GM-CSF were measured before treatment and on study days 155 and 351. Blood draws for testing biological effects were keyed to GM-CSF administration: days 0 (before), 15 (after 14 d on GM-CSF), 29 (after 14 d off GM-CSF), 155, and 351 (after 14 d on GM-CSF in the sixth and 13th cycle of treatment).

RESULTS

Of 53 patients enrolled, 43 were evaluable for the development of anti-GM-CSF antibodies. Of these, 93% developed binding antibodies and 42% developed both binding and neutralizing antibodies. The increase in the white blood cell count, percent eosinophils, or neopterin levels engendered by GM-CSF administration was abrogated or markedly decreased in patients with neutralizing antibodies but not in patients who developed only binding antibodies.

CONCLUSIONS

Ninety-three percent of patients with melanoma treated with GM-CSF as adjuvant therapy develop antibodies to GM-CSF. In those with neutralizing antibodies, a diminution of the biological effects of GM-CSF was observed. The development of neutralizing antibodies might also abrogate the potential clinical benefit of this treatment and should be considered in the design of future clinical trials.

The emerging roles of tumor-derived exosomes in hematological malignancies

Exosomes are small (30-150 nm) membranous vesicles of endocytic origin produced by all cells under physiological and pathological conditions. They have recently emerged as vehicles for intercellular transfer of molecular and genetic contents from parent to recipient cells. Exosome-mediated transfer of proteins or genes (RNA, miRNA, DNA) results in reprogramming of recipient cell functions. Exosomes carry and deliver information that is essential for health, and they participate in pathological events, including malignant transformation. Within the hematopoietic system, exosomes maintain crosstalk between cells located in the bone marrow compartment and at distant tissue sites. In hematological malignancies, tumor-derived exosomes (TEX) reprogram the bone marrow environment, suppress anti-leukemia immunity, mediate drug resistance and interfere with immunotherapies. TEX are also viewed as promising biomarkers of malignant progression and as potential therapeutic targets. The involvement of TEX in nearly all aspects of malignant transformation has generated much interest in their biology, mechanisms responsible for information transfer and the role they play in cancer escape from the host immune system.

Chondroitin sulfate proteoglycan-4 (CSPG4)-specific monoclonal antibody 225.28 in detection of acute myeloid leukemia blasts

Chondroitin sulfate proteoglycan-4 (CSPG4), a membrane-bound proteoglycan known to be expressed on the surface of malignant cells, has a restricted distribution in normal tissues. CSPG4 is a potential candidate tumor marker. We investigate CSPG4 expression on blasts in newly diagnosed acute myeloid leukemia (AML) patients and its relation with cytogenetic abnormalities and molecular markers known to have prognostic significance in this disease. Using hybridoma technology, we generated a specific monoclonal antibody (mAb), mAb 225.28, reactive with CSPG4. Blast samples obtained from the peripheral blood of newly diagnosed AML patients were analyzed for CSPG4 expression using the CSPG4-specific mAb and multiparameter flow cytometry. The results were correlated with cytogenetic and molecular characteristics of AML. CSPG4 was found to be expressed on a variable fraction of leukemic blasts in all AML patients with different leukemia morphology, including monoblastic cases. Reactivity of CSPG4-specific mAb with leukemic blasts was not limited to those with the rearranged MLL gene. CSPG4 was also expressed on AML blasts with a complex karyotype, FLT3 mutation, or NPM1 mutation. The results indicate that CSPG4 is expressed and detectable by flow cytometry using the mAb 225.28 on a proportion of blasts of all subtypes of AML irrespective of cytogenetic and molecular abnormalities. mAb 225.28 could be useful in detecting AML blasts by flow cytometry.

Isolation of Biologically Active Exosomes from Plasma of Patients with Cancer

A method for exosome isolation from human plasma was developed for rapid, high-throughput processing of plasma specimens obtained from patients with cancer. This method removes the bulk of plasma proteins associated with exosomes and can be used for comparative examinations of exosomes and their content in serial specimens of patients' plasma, allowing for monitoring changes in exosome numbers, profiles, and functions in the course of cancer progression or during therapy. The plasma-derived exosomes can be recovered in quantities sufficient for the characterization of their morphology by transmission electron microscopy (TEM), size and concentration by qNano, protein/lipid ratios, nucleic acid extraction, molecular profiling by Western blots or immune arrays, and functional assays.

Exosomes in Cancer: Another Mechanism of Tumor-Induced Immune Suppression

Exosomes are the smallest extracellular vesicles (EV) produced under physiological and pathological conditions by all cells and present in all body fluids. They are critical components of the intercellular communication network. Tumor cells release exosomes which are enriched in immunosuppressive molecules as well as biologically-active soluble factors and enzymes. Tumor-derived exosomes (TEX) interact with immune effector cells in the tumor microenvironment and in the circulation, deliver negative signals to these cells and interfere with their anti-tumor functions. By suppressing functions of immune effector cells, TEX promote tumor progression and facilitate tumor escape from the immune system. Thus, TEX can be viewed as immune checkpoint inhibitors. Silencing of TEX-mediated immune inhibition without disrupting the physiologically important cellular communication networks represents a considerable challenge. Current efforts are directed at achieving a better understanding of the role exosomes play in cancer progression and/or outcome and of molecular/genetic mechanisms responsible for immunoinhibitory activity of TEX.

Emerging Opportunities and Challenges in Cancer Immunotherapy

Immunotherapy strategies against cancer are emerging as powerful weapons for treatment of this disease. The success of checkpoint inhibitors against metastatic melanoma and adoptive T-cell therapy with chimeric antigen receptor T cells against B-cell-derived leukemias and lymphomas are only two examples of developments that are changing the paradigms of clinical cancer management. These changes are a result of many years of intense research into complex and interrelated cellular and molecular mechanisms controling immune responses. Promising advances come from the discovery of cancer mutation-encoded neoantigens, improvements in vaccine development, progress in delivery of cellular therapies, and impressive achievements in biotechnology. As a result, radical transformation of cancer treatment is taking place in which conventional cancer treatments are being integrated with immunotherapeutic agents. Many clinical trials are in progress testing potential synergistic effects of treatments combining immunotherapy with other therapies. Much remains to be learned about the selection, delivery, and off-target effects of immunotherapy used alone or in combination. The existence of numerous escape mechanisms from the host immune system that human tumors have evolved still is a barrier to success. Efforts to understand the rules of immune cell dysfunction and of cancer-associated local and systemic immune suppression are providing new insights and fuel the enthusiasm for new therapeutic strategies. In the future, it might be possible to tailor immune therapy for each cancer patient. The use of new immune biomarkers and the ability to assess responses to therapy by noninvasive monitoring promise to improve early cancer diagnosis and prognosis. Personalized immunotherapy based on individual genetic, molecular, and immune profiling is a potentially achievable future goal. The current excitement for immunotherapy is justified in view of many existing opportunities for harnessing the immune system to treat cancer.

Biological markers of prognosis, response to therapy and outcome in ovarian carcinoma

INTRODUCTION

Ovarian cancer (OvCa) is among the most common types of cancer and is the leading cause of death from gynecological malignancies in western countries. Cancer biomarkers have a potential for improving the management of OvCa patients at every point from screening and detection, diagnosis, prognosis, follow up, response to therapy and outcome.

AREAS COVERED

The literature search has indicated a number of candidate biomarkers have recently emerged that could facilitate the molecular definition of OvCa, providing information about prognosis and predicting response to therapy. These potentially promising biomarkers include immune cells and their products, tumor-derived exosomes, nucleic acids and epigenetic biomarkers. Expert commentary: Although most of the biomarkers available today require prospective validation, the development of noninvasive liquid biopsy-based monitoring promises to improve their utility for evaluations of prognosis, response to therapy and outcome in OvCa.

Plasma-derived exosomes in acute myeloid leukemia for detection of minimal residual disease: are we ready?

The recent emergence of plasma-derived exosomes as biomarkers of leukemic relapse has introduced the potential for more sensitive non-invasive monitoring of leukemia patients based on the molecular and genetic analysis of the exosome cargo. In principle, the protein, lipid, miRNA, mRNA or DNA profiles of exosomes in patients' plasma that associate with leukemic relapse can be identified. The diagnostic/prognostic value of these profiles could then be validated in prospective clinical studies. Here, we consider the potential of exosomes to fulfill the role of future biomarkers of minimal residual disease in AML. The rationale for developing exosome-based methodology for minimal residual disease detection is based on promising early observations. However, standards need to be established for evaluating exosome identity, isolation from body fluids, and assessment methods. The rapidly expanding knowledge of the exosome biology suggests that the exosome status as potential biomarkers may become clarified in the near future.